This study seeks to elucidate the site(s) of control of lipogenesis in liver and adipose tissue of rats caused by a low level of a dietary fat which is high (77%) in linoleate, 5% safflower oil. The acute response (less than 8 hours) of fatty acid biosynthsis to a single meal of the linoleate diet is being investigated in order to determine if linoleate exerts an effect on lipogenesis before there is a measureable effect on the activities of the lipogenic enzymes. The influence of dietary linoleate on some mitochondrial functions is being assessed by determining its effect on mitochondria used in reconstituting a cell-free lipogenic system and on the activity of pyruvate dehydrogenase. The effect of dietary linoleate on the rates of synthesis and degradation of fatty acid synthetase will be determined. The possibility is being investigated that dietary linoleate controls lipogenesis by regulating insulin either indirectly through a prostaglandin-c-AMP-insulin interrelationship or by directly binding insulin. In order to evaluate these biochemical responses to dietary linoleate, all experiments include cntrol rats fed a diet which contains 5% cocoa butter, a fat which is 3.5% linoleate, as well as rats fed a high-carbohydrate fat-free diet.